Abstract The molecular interactions and cooperative dynamics of tripropylene glycol (TPG) in ethanol solutions have been discussed using dielectric relaxation spectroscopy technique. The dielectric measurements have been carried for entire binary mixtures of TPG–ethanol at different temperatures (25 °C, 15 °C and 5 °C). Time domain technique in the frequency ranges of 10 MHz to 50 GHz have been employed for dielectric measurements. The dielectric parameters evaluated from the dielectric measurement and other parameters such as Kirkwood correlation factor, excess permittivity and thermodynamic parameter confirm the hetero molecular hydrogen bonding interaction among the TPG–ethanol molecules.